Gassing cheese products are generally characterized by the emission of carbon dioxide during their curing process. Packaging films used for packaging of such cheese must be able to allow carbon dioxide escape, so that a possible “ballooning” effect is avoided. At the same time, oxygen permeability should be as low as possible, so that the oxidation-deterioration of the cheese is minimized.
Heat shrinkable films are often used for gassing cheese packaging due to the good aesthetic appearance that heat shrinkability induces. High transparency of the pack is also important, so that possible consumers are attracted by the pack.
The majority of heat shrinkable films used in this area comprise PVDC as barrier layer. PVDC is difficult to extrude and quite easy to burn and deteriorate during the extrusion process.
PVDC formulations like for example described in prior art patents are commonly used.
Generally these PVDC formulations incorporate high percentage of plasticizers or stabilizers in order to increase the permeability to CO2. Common plasticizers/stabilizers are epoxidized compounds like epoxidized soybean oil, epoxidized linseed oil, etc. One negative effect is that these compounds tend to migrate from the PVDC layer to other layers, thus creating delaminations and, most dangerously, change of barrier properties as time passes. This is an undesirable phenomenon.
So, several features that should characterize a heat shrinkable film intended for use in packaging of gassing cheese are
1. High shrinkage
2. Excellent optics
3. Efficient heat sealability so that bags can be made
4. Avoidance of plasticizer use
5. Good processability of PVDC, no oxidation during extrusion
6. High CO2 permeability, not changing over time
7. High O2 barrier, not changing over time.
These features are matched with the PVDC combination of the present invention and with the heat shrinkable films we further advice.